Grinding machines



May 2, 1961 F. E. EDQv|sT GRINDING MACHINES Filed April l0. 1959 i a? mi, u

o :la ma y 6 Ile/2 IN VENTOR FLKE EVLD EDOVIST f v BYOZ/ZWM ATTORNEYS May 2, 1961 F. E. EDQvlsT 2,982,056

GRINDING MACHINES Filed April l0. 1959 2 Sheets-Sheet 2 .3L .33 .fi 1 32 INVENTOR FOLKE EVA/LD EDQVIST ATTORNEYS nited States Patent O frice Y2,982,056 l GRnsDlNG MAcrnNEs Folke Evald Edqvist, Hallspjallsgatan, p

' Goteborg, Sweden Filedl Apr. 10, 1959, ser. N0.- sos,s14 claims priority, application sweden Nov. '24, 195s 2 claims. (ci. s14s) The present invention relates to grinding machines of the kind wherein the ygrinding wheel is movable towards and away from the work piece by means of a piston displaceable in a` pneumatic cylinder, a substantially constant air pressure being maintained in one of the cylinder chambers situate'dpon eachV side of the piston, ywhile the pressure in the Vsecond cylinder chamber` is adjustable for obtaining the desired grinding pressurebetween 2,932,056 Patented May 2, 1961 to the invention with parts broken away to show the interior of the machine;

Fig. 2 is a partly broken plan view of the machine, and

Fig. 3 is a diagrammatic illustration` of the pneumatic system of the machine.

Numeral 1 designates a grindingrtable provided with clamps 2 for clamping a work piece onto the table. VThe outline of a steel billet 3 placed between the clamps 2` the bed .4 there is arranged a lbase structure 6 for a the grinding wheel and the work piece by means of a vvariable reducing valve connected to a compressed air conduit, said second cylinder chamber communicating with said reducing valve via a two-way valve which by means of an operating valve may be switched from a position in which it connects said second cylinder cham-V ber with saidreducingV valve to a position in which the cylinder `chamber is connected to an outlet.

1 Grinding machines of this type are used for removing the casting skin and glow scales from steel billets and slabs, and for other similar purposes where only the outermost surface layer of the work piece is to be removed together with surface cracks and impurities while maintaining the overall shape of the work piece. To this end the grinding wheel is movable towards and away from the Work piece so that it may follow the irregularities in the surface of the work piece. H-itherto known machines ofthis kind have the drawback, that the grind-V required limits.

. This drawback is overcome bythe present invention according to which an` air tank having considerably greater volume than the pneumatic', cylinder is connected to said second cylinder chamber., The pressure varia-V tions occurring in the cylinder chamber due to small displacements of the piston will thus bereduced to such an extent, that the grinding pressure may be' regarded as practically constant,` A Y `According to a preferred embodiment of the invention a valve is arranged betweenthe'air tank and said second cylinder chamber communicating therewith, said .v valve being operable by means of the operating valve vficesto keep the grindingpressure constant within the i in such a way that the connection between the cylinder chamber and the air tank is interrupted simultaneously with the two-way valve being switched to the position connecting the cylinder chamber with said outlet. Due to this arrangement the pressure in the air tank is maintained, so that the' machine `may be started again without delay. A l Y i l i IOne embodiment ofthe invention is illustrated in the accompanying drawings in which:

s* ,f!1Fig. l 'is aside v1ew of agrinding machine according cross slide 7 displaceable along a trackway on top of the base 6 transversely of the grinding table 1. For convenience, the end of the cross slide nearest to the grinding table will here be termed the front end. The cross slide car-ries at its front end a grinding wheel head 8 which is displaceable vertically for moving the grinding wheel 9 towards and away yfrom the grinding table.

The grinding wheel head 8 is supported by a parallellinkage arrangement comprising two upper arms 10, 10a and two llower arms 11, 11a. The upper and lower arms are swingably journalled on horizontal shafts 12 and 13, respectively, mounted transversely in the rear portion of the cross slide 7. At their opposite ends, the arms 10, 10a and 11, 11a are passed through slots in the front wa'll of the cross slide and pivotally connected to shafts 1-4 and `15, respectively, extending through the grinding wheel head 8. The upper arms 10, 10a are made shorter than the lower arms 11, 11a in order to provide accommodation in the rear portion of the cross slide for an electric motor 16 carried by the arms 10, 10a. The motor is arranged to drive the grinding wheel via the upper shaft 14 of the grinding Wheel head 8, said shaft being provided Iat one end with a number of V-pulleys 17 for V-belts 18 (indicated only in broken'lines) passed around a corresponding number of V-pulleys 19 on the motorV shaft. To the opposite end` of shaft 14 there are attached V-pulleys 20 for V-belts 21 passed around V- pu'lleys 22 onthe shaft of a gear box 23 from which the grinding wheel 9 is driven.

A pneumatic cylinder 24 is disposed in the cross slide 7 adjacent the front end thereof and extends vertically between the arms 10, 10a. The top end of the cylinder 24 is pivotally supported at the top `of the cross slide, and the piston rod 25 extending from the lower end of the cylinder is articulated to a cross piece 26 connected to the lower ar-ms 11, 11a. Thus, by raising the cylinder piston the grinding wheel head may be raised. The grinding pressure may also be adjusted byadjusting the air `or less. The pneumatic cylinder is operated from a control stand 27 placed in front of thev machine by means of valves and conduits which for the sake of clearness are not shown in Figs. 1 `and l2 but which will be described in detail herebelow with reference tofFig. 3.

Fig. 3 is a diagrammatic representation of the pneumatic system of the machine, `and to facilitate understanding of the operation of the machine there are also shown the parallel-linkage arms 10, 11 carrying the grinding wheel head. As already mentioned, the piston rod 25 of [a piston 28 displaceable in the pneumatic cylinder 24 is coupledto the arms 11, 11a. The cylinder 2 4 is divided by ythe piston 28 into two chambers, 29 and 30. Compressed air is fed tothe chamber Z9 of the cylinder from a feed pipe 31 by means of a conduit 32a, a reducing valve 33, a conduit 32b, a valve 34 and a conduit 32e. To the cylinder chamber 30 on the opposite side of the piston 28 air pressure is supplied from pipe 31 by means of a conduit 35a, a reducing valve 36, a conduit 35h, a valve 37 `and a conduit 35e. The cylinder chamber 30 communicates with an air tank 40 via a conduit 38a, a valve 39 and a conduit 38b. A branch conduit 41a is further connected to feed pipe 31 and con nects to a reducing valve 42 which by means of a conduit 41b is connected to a control valve 43 from which compressed air for opening the valves 36,l 37 and 39 is distributed by means of conduits 44, 4S and 46, respectively. Pressure reduction in the valve 36 `may be varied by varying the pressure in the control conduit 44. Thus, the valve 36 may be opened and closed by means of the control valve 43 and the air pressure in the outgoing conduit 35.?) of the valve 36 may be adjusted by adjusting the reducing valve 42 connected in the pressure conduit 41a, 41b leading to the control valve 43. When the control valve 43, which may be operated by means of a pedal 43a, is open the valves 36, 37 and 39 will thus be held open under the action of the pressure in the conduits 44, 45 and 46, respectively, so that compressed air is fed to the cylinder chamber 30 and the air tank y40 communicating therewith. The pressure in the two chambers 29 and 30 of the cylinder may be checked by means of pressure gauges 47 and 48, respectively, and is adjusted by means of the reducing valves 33 and 42, respectively, in such a way that the desired grinding pressure is obtained between the grinding wheel 9 and the work piece. The lower cylinder chamber 29 is provided with a springloaded outlet valve 49 which is adjusted in such a way that it will open if the pressure in chamber 29 rises above the desired value. Pressure variations in the chamber 30 caused by displacement of the piston 28 in the cylinder 24 will be very small thanks to the large volume of the air tank 40 connected to said chamber, so that the pressure in chamber 36 may `be regarded as practically con-y stant, independently of smaller variations in the position of the piston 28. In spite of the air tank a relatively large pressure variation may occur in chamber 30 if the piston is moved a greater distance upwardly under the influence of irregularities in the surface of the work piece. Such an increase in pressure is balanced by the reducing valve 36 which is provided with an outlet 36h to which the conduit 35h is connected if the pressure for which the valve 36 is adjusted is exceeded a certain amount. Due to the fact that the reducing valve 36 is arranged to be remote-controlled by means of the reducing valve 42 which controls the pressure in thetcontrol conduit 44 of the reducing valve 36, the latter may be mounted closely adjacent the cylinder 24, so that equalization of pressure takes place rapidly. The pressure in the cylinder chamber 29 is kept constant by means of the outlet valve 49. The grinding wheel 9 will thus follow all irregularities in the surface of the work piece while maintaining the chosen grinding pressure.

Upon closing of the operating valve 43 the valves 36, 37 and 39 will close, the conduit 35C to the cylinder chamber 30 thereby being connected to an outlet 37a on the valve 37, so that the cylinder chamber 30 will be put into communication with the surrounding air. The pressure in the air tank 4t) is maintained since the valve 39 between the cylinder chamber and the tank is closed simultaneously. The grinding wheel 9 will thus be raised rapidly from the work piece as a result of the piston 28 being displaced upwardly under the action of the pressure in the lower cylinder chamber 29. When the arms 10, 11 carrying the grinding wheel head 8 in this way have been swung to an upper end position, a cam 50 mounted on the lower arm 11 will cause the valve 34 to close, so that the compressed air feed to the cylinder chamber 29 is interrupted.

The operating valve 43 is also arranged for automatic cut-olf -in case the grinding wheel is lowered below a certain lowermost level. This cut-off is caused by an air impulse from a valve 51 which is connected to the feed pipe 31 bymeans of a conduit 52 and to the valve 43 by means of a conduit 53 and arranged to be actuated by a cam 54 movable together with the grinding wheel head and adjustable in vertical direction relative thereto. The air tank 40 is provided with anv out-let valve 40a, by means of which the tank may be emptied ifrneeded.

The invention is not limited to the embodiment hereinbefore described and as illustrated in the accompanying drawings, said embodiment being susceptible of various modifications with respect to its details, without departing from the spirit of the invention.

What I claim is: n

1. A grinding machine comprising -a support, a driven grinding wheel, means moveably connecting said grinding wheel to said support, a cylinder connected at one end to said support, a piston slideably mounted in said cylinder and dividing said cylinder into a pair of chambers, a rod connected to said piston, extending from the other end of said cylinder yand operatively connected to said connecting means for moving the same, a compressed air circuit connected to one chamber of said cylinder for maintaining a constant air pressure in said chamber, a `second circuit connected to said iirst-rnentioned circuit and the other of said chambers, a variable reducing valve connected in said second circuit, -a twoway valve in said second circuit between said reducing valve and said other chamber capable of admitting air to and exhausting air from said second chamber, an air tank having a considerably larger volume than said cylinder, an auxiliary circuit connecting said second chamber to said air tank, a valve interposed in said auxiliary circuit for controlling the passage of air therethrough, a control valve connected to said compressed air circuit, pneumatic means connecting said control valve to said two-way valve and said auxiliary circuit valve for operating the `same together for switching said two-way valve and auxiliary circuit valve from admitting air to said second chamber .and between said second chamber and said tank respectively to exhausting air from said second chamber `and closing the communication ybetween said second chamber and said tank for controlling the movement of ysaid grinding wheel relative to a work picce.

l2. A grinding machine as claimed in claim 1, wherein said reducing valve isV positioned adjacent said cylinder and 1s connected to said pneumatic means `for `being operated by said control valve.

References Cited in the tile of this patent UNITED STATES PATENTS 2,797,532 Lowe July 2, l957 

